1. Technical Field
The present invention relates to a turn bar (angle bar) apparatus of a rotary press used for back printing of a web or film and moving a continuous web paper for the rotary press.
2. Background Art
A conventional turn-bar apparatus A of this type is shown in FIG. 1, and the turn bar apparatus A is generally composed of an upstream side turn bar 1, a downstream side turn bar 2, an upstream side guide roller 3 disposed on an upstream side of the upstream side turn bar 1, a downstream side guide roller 4 disposed on a downstream side of the downstream side turn bar 2, and an intermediate roller 5 disposed between the turn-bars 1 and 2 at the side portion thereof. A web such as paper or film is engaged with and run through the upstream side guide roller 3, the upstream side turn bar 1, the intermediate roller 5, the downstream side turn bar 2 and the downstream side guide roller 4, in this order. During this running, the front and back surfaces of the web 6 is turned over and a tension is applied between the turn bars 1 and 2 is adjusted by the intermediate roller 5. Reference numeral 7 denotes an auxiliary guide roller.
Printing units, not shown, are disposed both upstream and downstream sides of the turn bar apparatus of the structure mentioned above.
In the turn bar apparatus A of the above structure, however, both the turn bars 1 and 2 are stationarily arranged, and the web 6 slidably runs along the surfaces of these turn bars 1 and 2. According to such structure, a running resistance at portions of these turn bars increases, which results in a large difference in tensions acting on the web 6 at inlet and outlet portions of the turn bar apparatus A. Moreover, the running resistance to the running web is not constant and the tension is hence changed. As a result, registerings of the printing units may be aberrant at the upstream and downstream sides.
In order to reduce such running resistance, in the conventional turn bar apparatus A, the turn-bars 1 and 2 are formed so as to have inner hollow structures having a plurality of fine holes formed to portions of the turn bars around which the web 6 is wound up, and air is blown out through these fine holes so that the web 6 floats above the surfaces of the turn bars 1 and 2 and runs in the floating state. In this structure, however, the positional accuracy of the web 6 is adversely affected by the air blowing strength and the registering accuracy at the printing operation is also adversely affected.
In another way for reducing the running resistance, in the conventional turn bar apparatus, a glass-bead bonded sheet, or high polymer plastic sheet having a good sliding performance, may be wound up around the surfaces of the turn bars 1 and 2. In this structure, the running resistance is not sufficiently reduced and such sheets have insufficient durability, thus also providing a problem.
In a further way of reducing the running resistance, the intermediate roller 5 may be formed so as to be freely or forcibly rotatable in the web running direction. In such a structure, however, when an intermediate roller 5 rotated with a constant speed by a driving device is used, the tension will be changed in a case where webs having different thicknesses run, resulting in a problem of degrading the registering performance at the printing operation.